Freshwater "anemone" ?

[redgrouse]

Last night I fed some live daphnia to my neon tetras.

The set up is a 90L planted tank with bogwood and gravel. it been up and running 3 months.

After the release of the daphnia I took a close look through the glass and noticed one or two daphnia struggling to move against the glass.

A closer examination revealed they had been snared by what looked like minute green thin anemone stuck to the glass. There were dozens of these microscopic organisms. I watched one catch a daphnia - it floated by and when touching the "tentacle" was stuck and held in place.

Any ideas what these are and most importantly will a few of these be detrimental to the fish?

Look forward to hearing from you

Richard

 

[Mr._Fishy]

I think I saw a topic on these a while back. I think the conclusion was they were worms that will eat food floating in the water column and are not harmful toward fish (with the possible exception of fry who could get caught). I am not 100% sure though so I would wait for someone else to come along.

 

[dizzied]

They're hydra. Never had any experience with them.

 

[redgrouse]

Thanks Dizzied

They are Hydra.

regards

Richard

 

[Colin_T]

Hydra are fine with any fish bigger than about 10mm long. However they will take fry and breed readily in the tank. They come in on plants and if they get into a breeding/ rearing tank they will catch and kill virtually all the fry in it.
A low dose of copper should kill them as does salt. If you don't plan on breeding fish then they aren't a real issue.